Lung cancer is the leading cause of cancer deaths in the United States. It claims more lives than colon, prostate and breast cancer combined. Over 196,000 patients are diagnosed with lung cancer each year in the United States and nearly 160,000 die of it. Yet, lung cancer patients are poorly serviced by current treatment protocols. Radiation therapy is a well-known option for the treatment of certain cancers, where ionizing radiation is directed to control or kill cancer cells (i.e., a malignant tumor) while limiting damage to healthy tissue. However, the treatment of lung cancers (and other cancers) may present an issue, for example, when the tumors move during irradiation.
Due to breathing by the patient, cancerous tumors within the lung are constantly in motion. Moreover, lung tissue is very sensitive to radiation, and damage can readily occur to healthy tissue surrounding the tumors within the lung. Often these tumors are found only once they are of substantial size (e.g., greater than 3 cm in diameter), such that patients are already quite ill when treatment begins. Since the tumor moves with each breath the patient takes, existing irradiation techniques generally increase the irradiation volume to account for this motion, thereby exposing increasing amounts of healthy tissue to potentially damaging radiation.
In image guided radiation therapy (IGRT), the radiation is guided to the treatment site based on images of the patient or surrogates attached to the patient. But since cancerous tumors in the lung are constantly moving due to breathing, precise targeting for IGRT proves to be a challenge. A new treatment modality for treating lung cancer, and other cancers where tumor motion may be an issue, is still needed.